took matplotlib sphinx extension back out of conf.py to prevent errors during RTD generation
took matplotlib sphinx extension back out of conf.py to prevent errors during RTD generation

dpshelio/sunpy,Alex-Ian-Hamilton/sunpy,dpshelio/sunpy,Alex-Ian-Hamilton/sunpy,mjm159/sunpy,dpshelio/sunpy,Alex-Ian-Hamilton/sunpy,mjm159/sunpy